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Reactor neutrino experiment
1
�e
Flux @ Reactor Pee @ far detector �e
�e + p� e+ + n
Mass Hierarchy determina;on with
E� � Evis + 0.8MeV
Oscilla;on
2
Mass Hierarchy difference
�e � �e
Energy distribu;on @ far detector
3
10000 20000 30000 40000
30 km NH IH
2000 6000
10000 14000 40 km NH
IH
1000 3000 5000 7000
dN /
dEi [
1/M
eV]
50 km NH IH
0 1000 2000 3000 4000
2 3 4 5 6 7 8
Ei [MeV]
60 km NH IH
�e
Obstacle1:
4
@ < 30 km, the NH-‐IH difference is totally absorbed by a small shiM of
within its uncertainty.
We need a far detector at L > 30 km
�|�m231|
�|�m231|
Obstacle2: finite Energy Resolu;on
5
b: systematic error parta: statistical error part
AMer smearing with the detector Energy resolu;on, the NH-‐IH difference Can be absorbed again.
�E
E=
�����
a�E/MeV
�2
+ b2
Upper limit on the Energy Resolu;on
Sensi;vity for mass hierarchy
6
0
2
4
6
8
10
12
14
10 20 30 40 50 60 70 80 90 100
(6r
2 ) min
L [km]
b = 0
a = 2% NH IH
3% NH IH
4% NH IH
5% NH IH
6% NH IH
20 GW 5kton 5 years
a < 3% for
�E
E=
�����
a�E/MeV
�2
+ b2
Op;mal L ~ 50 km
(��2)min > 9
Systema;c Error of Resolu;on
7
0
2
4
6
8
10
12
14
10 20 30 40 50 60 70 80 90 100
(6r
2 ) min
L [km]
(a, b) = (2, 0) NH IH
(2, 0.5) NH IH
(2, 0.75) NH IH
(2, 1) NH IH
�E
E=
�����
a�E/MeV
�2
+ b2
b < 1% for
20GW 5kton 5 years
Larger b Shorter op;mal L
(��2)min > 9
8
0.7
0.75
0.8
0.85
0.9
0.95
1
0 10 20 30 40 50
C. L
.
(6r2)min
×1
×2 ×3 ×4
×1
×2
×3
×4
×6×8 ×10
L = 50 km
(a, b) = (2, 0.5): NH IH
(3, 0.75): NH IHNo Fluctuation
Considering fluctua;on of data
20GW 5kton 5 years �n
Parameter measurement
9
0.51.01.52.0
sin22e12
×10-2(a, b) = (3, 0.5) NH
IH(3, 1) NH
IH(6, 1) NH
IH
1234 sin22e13
×10-3
0.51.01.5
Sta
tist
ical
Un
cert
ain
ty
6m221
×10-6eV2
0246
10 20 30 40 50 60 70 80 90 100
L [km]
|6m231|
×10-5eV2
Parameter measurements are not sensi;ve to the Energy resolu;on
~ 0.5% level of uncertain;es can be achieved for sin2 2�12
|�m231|
�m221
OutLook
• Consider the energy scale uncertainty of the detector
• Find a suitable place in Korea, taking into account mul;-‐reactor interference
• MH determina;on with Long baseline neutrino oscilla;on, i.e., T2KK
10
Other On-‐going Projects • QCD Mul;-‐jet genera;on with MadGraph – pp > 5 jets becomes possible, but not 6 jets – Now improving phase space integra;on (MadEvent) • gg > 4g is checked with new integra;on method • gg > 5 g under going (want to go up to gg > 7g )
• Implementa;on of spin-‐3/2 par;cle into FeynRule/MadGraph, FR/CalcHep – Almost done, now in valida;on phase
11
12
Thank you
Summary • We study the sensi;vity of a future medium baseline reactor neutrino experiment for MH determina;on.
• For 20 GW 5kton 5 years exposure,
– op;mal baseline length ~ 50 km
– < 3% sta;s;cal & < 1% systema;c errors of Energy Resolu;on is required
– 0.5% level of accuracy for Neutrino Parameters
13
* This study gives the minimum requirement for the energy resolu;on. * More realis;c study is very sensi;ve to the environment, such as distribu;on of reactors within ~100 km from the far detector (J.Evslin et.al, arXiv:1209.2227).
14
-0.25 0
0.25 0.5 sin22e12
2% NH IH
3% NH IH
6% NH IH
-0.25 0
0.25 0.5 sin22e13
-0.25 0
0.25 0.5
pull
fact
or
6m221
-0.25 0
0.25 0.5
|6m231|
-0.25 0
0.25 0.5
10 20 30 40 50 60 70 80 90 100L [km]
fsys
15
-10 0 10 20 30
50
100
150
(��2)min
�E
E=
�����
2%�E/MeV
�2
+ (0.5%)2
L = 50km1000 experiments
(��2)min = 11.2
�(��2)min = 7.1
16
-5
0
5
10
15
20
10 20 30 40 50 60 70 80 90 100
(6r2 ) m
in
L [km]
20GWth, 5kton (12.00% proton), 5 years, (bEvis/Evis)2 = ( (a / 3Evis)
2 + b2 )%
(a, b) = (2, 0.5) NH IH
Determina0on of mass hierarchy with reactor neutrino experiment
Yoshitaro Takaesu
KIAS/KNRC
17
In collabora0on with S.F. Ge, N. Okamura and K. Hagiwara
Introduc;on
• DayaBay and RENO observed large • There is a possibility that neutrino mass hierarchy is determined by observing reactor neutrino oscilla;on at km away
• In this talk, I discuss the sensi;vity of the future medium baseline reactor experiments for determining mass hierarchy
18
�13
O(10)
Mass Hierarchy
19
If we assume there are 3 types of netrinos, there are 6 possible mass hierarchies.
We know
There are two possibili;es leM, NH and IH.
Which one is realized in Nature?
Long standing and big ISSUE.
�m221 = m2
2 �m21 � 7.5� 10�5
�m221 < |�m2
31| � 2.3� 10�3
m1
m2
m3
m1
m2
m3
Normal Hierarchy (NH)
Inverted Hierarchy (IH)
|�m231|
�m221
We es;mate – Op;mal baseline length
– Energy resolu;on required – Expected uncertain;es of neutrino parameters
Assuming an experiment with 20 GW 5kton (12% free proton) 5 years exposure.
20
Analysis method
21
We calculate the neutrino energy distribu;on for NH or IH,
Energy Resolu;on smearing (Gaussian)
We then perform the standard analysis to this “data” (next slide).
dNNH(IH)
dEobs=
NpT
4�L2
�dE�
dN
dE�Pee(L, E�)�IBD(E�)G(Etrue �Eobs, �E)
* corresponds to the averaged observed distribu;on. We don’t consider the fluctua;on of data from experiment to experiment in this talk.
dNNH(IH)
dEobs
We introduce bining and prepare “data”, the number of events in each bin.
NNH(IH)i =
� Eobsi+1
Eobsi
dEobs dNNH(IH)
dEobs (i = 1, · · · , nbins)
�2
Analysis method -‐
22
The sensi;vity to determine MH:
�2Analysis
Results
23